Can someone please explain to me what .io1 files are and what program I can view them in?

probably some kind of backup or archive file

There is no real "standard" for file extensions just an accepted convention so programmers often make up their own to suit their purpose.

Where's the mystery file come from?

If in doubt, I tend to try a text editor, but if that doesn't work it's likely that you can't open it. Obviously check Google to see if the extension is well-known, but I couldn't find anything on there about it...

Chris is probably right, but I expect the location on your computer (?) is likely to provide some kind of clue...

Originally Posted by Hoosier_Buddy

Can someone please explain to me what .io1 files are and what program I can view them in?

First of all, I don't promote pirating stuff, but here you are.

2. DVD Shrink file. An ISO (DVD) image that has been split into multiple parts by DVD Shrink in order to overcome limitations on the maximum file size imposed by the limitations of FAT 32 file systems. Each file is approximately 1GB in side, subsequent files will be .i01, .i02 etc and there should also be a .mds file that contains information on the parts.

Link Here.

Nick

Here is one thing that they are

The second file of a group of disk image files saved by DVD Shrink, a program that compresses DVD-Video data to fit on a single DVD-R disc; usually saved as part of a sequence of files; for example, the first file has a .I00 extension, the second file ends in I01, the third file has a .I02 extension, etc.

Originally Posted by goheadtry

Here is one thing that they are

The second file of a group of disk image files saved by DVD Shrink, a program that compresses DVD-Video data to fit on a single DVD-R disc; usually saved as part of a sequence of files; for example, the first file has a .I00 extension, the second file ends in I01, the third file has a .I02 extension, etc.

Ha! Thanks for the direct quote

Nick